I feel that when you pay the experience bonus and then the mana bonus for an upgrade, you shouldn't have to pay it every single level... And there should be a way to increase mana gaining speed, so that if you upgrade max mana bonus, you can also recharge a little faster...
I think there should be a theme to it.. that way people can "win" more, because even though the animations are cute, the game becomes less fun if you constantly lose. Also, more time would make it a little easier..
 "Epic War 2"){kind=icon}
 "Hangman Extreme!"){kind=icon}